A 39-byte-long machine language routine to do something amusing to the Commodore 64's screen display.
After the PRG file has loaded, enter
SYS 828
to activate it.
You may then wish to select a different text colour using the colour keys (Ctrl+1, Ctrl+2, etc.)
The file was originally created (circa 1987) under the name "bored cursor.ml". It was called by the somewhat more clever name "The PETulant Cursor" when it was resurrected and used as a 6502 assembly example in 2008.